1. Field of the Invention
This invention relates to a zoom lens capable of effecting a macro (close-up) operation, and in particular to the mechanical operating device thereof.
2. Description of the Prior Art
Various focusing devices of zoom lenses capable of focusing to the so-called macro area just beyond the close distance position in the normal photography area which enables zoom magnification change have been proposed and are already known.
However, in any of the above-described zoom lenses, there are provided both a focusing member for the normal photography area and a focusing operating member for the macro area (an operating member serving also for zoom magnification change). Therefore, in the known focusing devices of this type, when photography is to be continuously effected from the normal photography area to the macro area or from the macro area to the normal photography area, the two operating members must be operated cooperatively. Accordingly, the operation for focusing is complicated and quick focusing cannot be accomplished and in addition, the focusing is discontinuous and this leads to the possibility of missing the opportunity to photograph an object in motion whose distance gradually changes.
A zoom lens in which zoom magnification change and focusing from the normal photography area to the macro area can be accomplished by an operating member is also known, for example, from U.S. Pat. No. 4,448,496. In the above-described prior art, there is shown a zoom lens in which focusing in the normal photography area is accomplished by rotating an operating member and subsequently focusing in the macro area can be accomplished by further rotation of the operating member beyond the normal photography area. However, back-lash is liable to occur in the connecting mechanism for macro photography change-over, and in the macro area wherein any slight adjustment error may lead to an extreme out-of-focus condition, focusing becomes unstable and inaccurate. Further, during focusing in the macro area, the lens for normal area adjustment is also greatly moved axially beyond the close distance position and therefore, not only the lens aperture becomes great, but also the aberrations; particularly, the curvature of image field of the optical system is increased.